import java.util.Scanner;

public class Ex5_36{
	public static void main(String[] args){
		Scanner input = new Scanner(System.in);
		System.out.print("Enter the number of sides and the side: ");
		int n = input.nextInt();
		double s = input.nextDouble();
		System.out.printf("The area is %.2f\n", area(n,s));
	}

	public static double area(int n, double side){
		return n*side*side/(4*Math.tan(Math.PI/n));
	}
}